diff --git a/parser/html/nsHtml5Parser.cpp b/parser/html/nsHtml5Parser.cpp
index b647d26fef1..0d7cc206c86 100644
--- a/parser/html/nsHtml5Parser.cpp
+++ b/parser/html/nsHtml5Parser.cpp
@@ -12,7 +12,7 @@
 #include "nsHtml5TreeBuilder.h"
 #include "nsHtml5AtomTable.h"
 #include "nsHtml5DependentUTF16Buffer.h"
-#include "nsIInputStreamChannel.h"
+#include "nsNetUtil.h"
 
 NS_INTERFACE_TABLE_HEAD(nsHtml5Parser)
   NS_INTERFACE_TABLE2(nsHtml5Parser, nsIParser, nsISupportsWeakReference)
@@ -218,7 +218,13 @@ nsHtml5Parser::Parse(const nsAString& aSourceBuffer,
     mExecutor->SetParser(this);
     mTreeBuilder->setScriptingEnabled(mExecutor->IsScriptEnabled());
 
-    mTreeBuilder->setIsSrcdocDocument(IsSrcdocDocument());
+    bool isSrcdoc = false;
+    nsCOMPtr<nsIChannel> channel;
+    rv = GetChannel(getter_AddRefs(channel));
+    if (NS_SUCCEEDED(rv)) {
+      isSrcdoc = NS_IsSrcdocChannel(channel);
+    }
+    mTreeBuilder->setIsSrcdocDocument(isSrcdoc);
 
     mTokenizer->start();
     mExecutor->Start();
@@ -682,7 +688,13 @@ nsHtml5Parser::Initialize(nsIDocument* aDoc,
 void
 nsHtml5Parser::StartTokenizer(bool aScriptingEnabled) {
 
-  mTreeBuilder->setIsSrcdocDocument(IsSrcdocDocument());
+  bool isSrcdoc = false;
+  nsCOMPtr<nsIChannel> channel;
+  nsresult rv = GetChannel(getter_AddRefs(channel));
+  if (NS_SUCCEEDED(rv)) {
+    isSrcdoc = NS_IsSrcdocChannel(channel);
+  }
+  mTreeBuilder->setIsSrcdocDocument(isSrcdoc);
 
   mTreeBuilder->SetPreventScriptExecution(!aScriptingEnabled);
   mTreeBuilder->setScriptingEnabled(aScriptingEnabled);
@@ -708,20 +720,3 @@ nsHtml5Parser::ContinueAfterFailedCharsetSwitch()
   mStreamParser->ContinueAfterFailedCharsetSwitch();
 }
 
-bool
-nsHtml5Parser::IsSrcdocDocument()
-{
-  nsresult rv;
-
-  bool isSrcdoc = false;
-  nsCOMPtr<nsIChannel> channel;
-  rv = GetChannel(getter_AddRefs(channel));
-  if (NS_SUCCEEDED(rv)) {
-    nsCOMPtr<nsIInputStreamChannel> isr = do_QueryInterface(channel);
-    if (isr) {
-      isr->GetIsSrcdocChannel(&isSrcdoc);
-    }
-  }
-  return isSrcdoc;
-}
-
diff --git a/parser/html/nsHtml5Parser.h b/parser/html/nsHtml5Parser.h
index 5d4d30e2a51..a46448e33ca 100644
--- a/parser/html/nsHtml5Parser.h
+++ b/parser/html/nsHtml5Parser.h
@@ -258,8 +258,6 @@ class nsHtml5Parser : public nsIParser,
      */
     void ParseUntilBlocked();
 
-    bool IsSrcdocDocument();
-
   private:
 
     // State variables
diff --git a/parser/html/nsHtml5StreamParser.cpp b/parser/html/nsHtml5StreamParser.cpp
index cdac25546e5..f6af085ee58 100644
--- a/parser/html/nsHtml5StreamParser.cpp
+++ b/parser/html/nsHtml5StreamParser.cpp
@@ -26,9 +26,9 @@
 #include "nsINestedURI.h"
 #include "nsCharsetSource.h"
 #include "nsIWyciwygChannel.h"
-#include "nsIInputStreamChannel.h"
 #include "nsIThreadRetargetableRequest.h"
 #include "nsPrintfCString.h"
+#include "nsNetUtil.h"
 
 #include "mozilla/dom/EncodingUtils.h"
 
@@ -877,7 +877,14 @@ nsHtml5StreamParser::OnStartRequest(nsIRequest* aRequest, nsISupports* aContext)
   bool scriptingEnabled = mMode == LOAD_AS_DATA ?
                                    false : mExecutor->IsScriptEnabled();
   mOwner->StartTokenizer(scriptingEnabled);
-  mTreeBuilder->setIsSrcdocDocument(IsSrcdocDocument());
+
+  bool isSrcdoc = false;
+  nsCOMPtr<nsIChannel> channel;
+  nsresult rv = GetChannel(getter_AddRefs(channel));
+  if (NS_SUCCEEDED(rv)) {
+    isSrcdoc = NS_IsSrcdocChannel(channel);
+  }
+  mTreeBuilder->setIsSrcdocDocument(isSrcdoc);
   mTreeBuilder->setScriptingEnabled(scriptingEnabled);
   mTreeBuilder->SetPreventScriptExecution(!((mMode == NORMAL) &&
                                             scriptingEnabled));
@@ -913,7 +920,7 @@ nsHtml5StreamParser::OnStartRequest(nsIRequest* aRequest, nsISupports* aContext)
   NS_ASSERTION(!mLastBuffer, "How come we have the last buffer set?");
   mFirstBuffer = mLastBuffer = newBuf;
 
-  nsresult rv = NS_OK;
+  rv = NS_OK;
 
   // The line below means that the encoding can end up being wrong if
   // a view-source URL is loaded without having the encoding hint from a
@@ -1672,20 +1679,3 @@ nsHtml5StreamParser::MarkAsBroken()
     NS_WARNING("failed to dispatch executor flush event");
   }
 }
-
-bool
-nsHtml5StreamParser::IsSrcdocDocument()
-{
-  nsresult rv;
-
-  bool isSrcdoc = false;
-  nsCOMPtr<nsIChannel> channel;
-  rv = GetChannel(getter_AddRefs(channel));
-  if (NS_SUCCEEDED(rv)) {
-    nsCOMPtr<nsIInputStreamChannel> isr = do_QueryInterface(channel);
-    if (isr) {
-      isr->GetIsSrcdocChannel(&isSrcdoc);
-    }
-  }
-  return isSrcdoc;
-}
diff --git a/parser/html/nsHtml5StreamParser.h b/parser/html/nsHtml5StreamParser.h
index 21f4726859a..8ac3f638e6e 100644
--- a/parser/html/nsHtml5StreamParser.h
+++ b/parser/html/nsHtml5StreamParser.h
@@ -202,8 +202,6 @@ class nsHtml5StreamParser : public nsIStreamListener,
      */
     void SetViewSourceTitle(nsIURI* aURL);
 
-    bool IsSrcdocDocument();
-
   private:
 
 #ifdef DEBUG